Leonardo da Vinci Medicine and Its Lasting Impact on Health

Leonardo da Vinci’s medical work, carried out largely between 1489 and 1513, produced some of the earliest accurate descriptions of human anatomy, cardiovascular function, and disease processes that modern science has since confirmed. He dissected more than 30 human bodies, described the heart as a four-chambered muscle, gave what is likely the first recorded account of atherosclerosis, and pioneered visualization techniques that anticipated methods used in medicine centuries later. Because his notebooks were never published during his lifetime, the influence took a strange path: some discoveries had to be made all over again by later researchers, while others, once rediscovered, proved so precise that they reshaped how physicians understood the body.

Dissecting by Candlelight

Leonardo’s anatomical investigations were grounded in hands-on dissection at a time when cutting open human bodies was legally restricted and culturally unsettling. Working in the crypt of Santa Maria Nuova hospital in Florence, he dissected more than 30 bodies of both sexes and all ages, often performing his work at night by candlelight. He paid grave robbers to supply corpses and would meticulously tease away minute particles of flesh and muscle to expose the smallest blood vessels, continuing until the corpse was too dismembered to permit further study.¹ This was not idle curiosity. Leonardo approached each dissection with specific questions about how organs functioned, how blood moved, and how the body’s mechanical parts worked together. He was driven by the conviction that understanding the body’s structure was inseparable from understanding its function, a principle that remains foundational in medical education.

His early anatomical studies were influenced by the ancient Greek physician Galen, whose texts had dominated medicine for over a thousand years. Leonardo initially accepted some Galenic ideas about anatomy, and several of his early drawings reflect structures Galen described in animals rather than humans.² As his dissection experience grew, though, he increasingly trusted his own eyes over received authority. That shift from textbook orthodoxy to direct observation was itself a significant contribution, setting a precedent for the empirical approach that would come to define modern medicine.

The Heart and Blood Vessels

Leonardo recognized the heart as a four-chambered muscle with two upper chambers (auricles) and two lower chambers (ventricles), a description that was remarkably accurate for his era.¹ At a time when many physicians still thought the heart was a two-chambered organ or a simple furnace that heated the blood, Leonardo’s structural understanding was centuries ahead. He studied the heart valves, the coronary vessels, and the way blood swirled through the aorta with a detail that would not be matched until the age of modern cardiology.

One of his most striking cardiovascular insights involved the sinuses of Valsalva, the small bulges at the root of the aorta just above the aortic valve. Leonardo observed, drew, and wrote about eddy currents forming in these sinuses, noting that the swirling flow helped the valve leaflets close properly after each heartbeat. This observation was essentially forgotten for centuries. Modern fluid dynamics studies have confirmed that the vortices Leonardo described do play an important role in aortic valve closure, exactly as his drawings suggested.³ Cardiac surgeons designing prosthetic aortic valves have drawn on this understanding. The fact that a Renaissance artist-engineer figured out a fluid dynamics problem that medical science would not formally revisit for about 400 years is one of the more remarkable stories in the history of cardiology.

The First Recorded Description of Atherosclerosis

Leonardo’s dissections were not limited to healthy anatomy. When he dissected the body of a man reportedly around 100 years old, he noticed that the blood vessels were thickened, narrowed, and hardened. He described how the vessel walls in elderly people differed from those in younger bodies, producing what is considered the first recorded description of atherosclerosis. He also noted changes in the man’s liver consistent with what we now call cirrhosis.⁴

This matters because atherosclerosis is now understood to be the leading cause of heart attacks and strokes worldwide, and the recognition that aging blood vessels undergo specific physical changes was a prerequisite for modern cardiovascular medicine. Leonardo did not have the concept of cholesterol plaques or the cellular biology behind arterial disease, but he saw the physical reality and documented it. His observation that the vessels of the old were structurally different from the vessels of the young was a genuine pathological finding, made at a time when disease was still widely attributed to imbalances of bodily humors rather than to changes in specific tissues.

Mapping the Brain with Wax

Leonardo’s neuroanatomy work is especially impressive because the brain is notoriously difficult to study through dissection alone. Soft brain tissue loses its shape quickly after death, making it hard to visualize the internal cavities. Leonardo solved this problem with an ingenious technique: he injected molten wax into the ventricles of animal brains, waited for it to solidify, and then removed the surrounding tissue to reveal a three-dimensional cast of the ventricular system.⁵ His initial experiments, conducted between roughly 1506 and 1508, used the heads of horses and oxen. He documented the procedures in careful detail, noting that he inserted tubes into the ventricles, used self-constructed syringes to inject the wax, and included narrow air vents to ensure the wax filled the cavities completely.⁶

This represents the first known use of a solidifying material to define the shape and size of an internal body structure.⁷ The technique would not be used on human brains until 1918, when the neurosurgeon Walter Dandy developed air-cast ventriculography to visualize the brain’s internal spaces in living patients.⁸ Dandy’s work was a milestone in neurosurgery, but the underlying concept of casting internal cavities to understand their shape had a four-century head start in Leonardo’s notebooks. Leonardo also made discoveries in neuroanatomy proper, including descriptions of the frontal sinus and the meningeal vessels, and he was reportedly the first person to pith a frog, a technique used to study nervous system function.⁷

How Breathing Actually Works

Leonardo’s investigations of the lungs and chest mechanics produced insights that were not widely appreciated until modern respiratory physiology caught up. He studied the mechanics of breathing in detail, including the action of the ribs and diaphragm during inhalation and exhalation. He was the first person to understand that the internal and external intercostal muscles, the muscles running between the ribs, have distinct and different roles in expanding and compressing the chest.⁹ He also had original ideas about how air flows through the airways, treating the problem as one of fluid mechanics rather than simply describing the tubes’ shapes.

This kind of functional thinking, asking not just “what does this structure look like” but “how does this structure move and what does the movement accomplish,” was rare in Renaissance anatomy. Most anatomists of the period were content to describe structures. Leonardo treated the body as a machine whose parts had mechanical purposes, an approach that aligns closely with how modern physiology and biomedical engineering operate.

Bones, Muscles, and the Body as a Machine

Around 1510, Leonardo produced an extraordinary set of drawings that depict the form and function of bones and muscles in meticulous mechanical detail. He likely collaborated during this period with Marcantonio della Torre, a young anatomist from Padua.¹⁰ His drawings show muscles as lines of force acting on the skeleton, treating the body as a system of levers and pulleys. He compared human leg anatomy with that of horses, analyzing their differences in terms of movement and mechanical efficiency.¹¹

This comparative approach, studying animal and human anatomy side by side to understand how form relates to function, anticipates the field of comparative anatomy that would develop formally in the eighteenth century. More immediately, Leonardo’s mechanical view of muscle action is a direct ancestor of modern biomechanics, the field that informs everything from orthopedic surgery to athletic training to prosthetic design. His idea that you could understand human movement by analyzing the forces muscles exert on bones is essentially the starting premise of contemporary movement science.

Vision, Reproduction, and the Scope of His Curiosity

Leonardo’s medical interests extended well beyond the heart and brain. He studied the eye extensively, describing how light rays were refracted and reflected within it. His anatomical understanding of the eye was imperfect, and that limited how far he could take his optical theories, but he was the first person to compare the eye to a pinhole camera.¹² That comparison became a foundational analogy in the study of vision and persists in introductory optics teaching to this day.

He also had a particular interest in reproduction and genitourinary anatomy, producing detailed studies of fetal development and the reproductive organs.¹³ His drawings of the fetus in the womb are among the most famous images in the history of anatomy. While some of these drawings contain errors rooted in the limited understanding of his era, they represent a serious attempt to understand human development through direct observation rather than philosophical speculation. The breadth of Leonardo’s medical inquiries is itself part of his legacy: he treated the body as a unified system where understanding the heart required understanding the blood vessels, which required understanding the aging process, which connected to the mechanics of blood flow. That integrative view is central to how medicine thinks about the body today.

Reinventing How the Body Could Be Shown

Perhaps Leonardo’s most enduring contribution to medicine is not any single anatomical finding but the way he depicted what he found. Before Leonardo, anatomical illustrations were crude and schematic, often little more than diagrams with labels. Leonardo introduced techniques that transformed medical illustration into a tool for understanding. He drew cross-sections of the body in multiple planes, created “exploded” views showing disassembled body parts in spatial relation to one another, and used transparency and shading to convey three-dimensionality on a flat page.¹⁴

These techniques are not historical curiosities. Modern anatomical atlases, surgical planning software, and medical education tools use cross-sectional views, exploded diagrams, and three-dimensional rendering that trace their conceptual lineage to what Leonardo pioneered. The idea that you could rotate a structure in your mind, see it from multiple angles, and understand how its parts fit together is something Leonardo brought to anatomy from his training as an artist and engineer. Medical illustration as a field essentially begins with him, and the visual language he developed remains the foundation for how anatomy is taught and communicated.

Why His Medical Work Disappeared for Centuries

The strange tragedy of Leonardo’s medical contributions is that almost none of them influenced medicine during the centuries when they could have made the most difference. Leonardo never published his anatomical notebooks. After his death in 1519, the approximately 7,000 pages of his notes passed through various hands, were scattered, lost, and in some cases deliberately hidden. His anatomical drawings were not widely seen by physicians or scientists until they were systematically studied in the nineteenth and twentieth centuries.

This means that many of his discoveries had to be made independently by later researchers who had no access to his work. Andreas Vesalius published his landmark anatomy textbook in 1543, roughly 30 years after Leonardo’s most productive anatomical period, without any knowledge of Leonardo’s far more detailed drawings. William Harvey described the circulation of blood in 1628, unaware that Leonardo had already grasped key elements of how blood moved through the heart and vessels. The result is that Leonardo’s medical legacy is less a chain of influence and more a case of parallel discovery confirmed in hindsight. When modern researchers examined his notebooks, they were astonished to find that he had anticipated findings that took centuries to establish through the normal channels of published science.

Where Modern Medicine Has Caught Up

The twentieth and twenty-first centuries have produced several striking moments of Leonardo’s work being validated by modern technology. His observations about vortex formation in the aortic sinuses, long dismissed as artistic speculation, were confirmed by engineering studies using flow visualization techniques.³ His descriptions of how the intercostal muscles operate during breathing align with what electromyography studies have since measured.⁹ His wax-cast technique for the brain ventricles anticipated methods that neurosurgeons would not use clinically until 1918.⁸

None of this means Leonardo was infallible. He made errors, some of them significant. His early drawings of the heart show features borrowed from Galen’s descriptions of animal hearts rather than human ones. His understanding of how blood circulated was incomplete; he did not grasp the pulmonary circuit the way Harvey later would. His embryological drawings contain inaccuracies that reflect the limits of what he could observe without a microscope. But the pattern of his work, direct observation, mechanical reasoning, precise visual documentation, repeated dissection to verify findings, reads as a prototype of the scientific method applied to medicine. The errors matter less than the approach, which proved to be the right one. Modern medicine does not build on Leonardo’s specific findings so much as it operates according to the principles he was among the first to embody: look at the body directly, think about it mechanically, draw what you see with ruthless accuracy, and trust your observations over inherited dogma.

Comparative Anatomy and the Animal Connection

Leonardo did not limit himself to human dissection. He dissected horses, bears, oxen, frogs, and other animals, and he routinely compared animal and human structures to understand how form related to function. His drawings of bear paws, horse legs, and ox brains were not idle sketches but systematic comparisons, placing human and animal anatomy side by side to highlight similarities and differences in movement and structure.¹¹ His brain-casting experiments, for instance, were conducted on ox and horse heads precisely because these were more readily available than human specimens and allowed him to refine his technique before attempting it on rarer human material.⁶

This habit of moving between species created both strengths and weaknesses. On the strength side, it gave Leonardo a broader perspective on how bodies are built, and his comparative drawings influenced later thinkers who formalized comparative anatomy as a discipline. On the weakness side, it sometimes led him to project animal features onto human anatomy, as when his early heart drawings included structures he had observed in oxen but that do not exist in human hearts. The tension between animal models and human anatomy is, in a sense, still alive in medicine today. Preclinical research relies heavily on animal models, and the question of when findings in one species can be safely applied to another remains one of the ongoing challenges of biomedical science. Leonardo encountered that challenge 500 years ago and dealt with it about as well as anyone could without modern tools.

1
The American Journal of Cardiology. Leonardo da Vinci and Medicine
2
PubMed Central. The influence of ancient Greek thought on fifteenth century anatomy: Galenic influence and Leonardo da Vinci
3
The Annals of Thoracic Surgery. Leonardo da Vinci and the sinuses of Valsalva
4
PubMed Central. Leonardo da Vinci on atherosclerosis and the function of the sinuses of Valsalva
5
The Lancet. Leonardo da Vinci’s studies of the brain
6
Frontiers in Neuroanatomy. Leonardo di ser piero da Vinci–a bridge between ancient and post-Galenic anatomy based on studies of the ventricular system of the brain
7
Cell Press (Trends in Neurosciences). Leonardo da Vinci’s research on the brain
8
PubMed. From the wax cast of brain ventricles (1508-9) by Leonardo da Vinci to air cast ventriculography (1918) by Walter E. Dandy
9
PubMed. Leonardo da Vinci: engineer, bioengineer, anatomist, and artist
10
Biological Theory. Revisiting Leonardo on Muscles: Intimations of Mathematical Biology and Biomechanics
11
PubMed Central. Leonardo da Vinci’s Animal Anatomy: Bear and Horse Drawings Revisited
12
PubMed. Studies of vision by Leonardo da Vinci
13
PubMed Central. The Renaissance of Reproductive Science: Leonardo da Vinci’s Anatomical Contributions
14
Translational Research in Anatomy. Leonardo da Vinci: In search of the seat of the soul – Reflections on the anatomical and neuroanatomical explorations of a great master